Do not mix up the grammatical feature (grammatical noun class = grammatical gender) with the biological feature (belonging of a living being to a biological gender)
In German grammar the grammatical gender is a property of a noun or pronoun. (In englisch nouns do not have a gender, only pronouns.) The grammatical gender is not a property of the thing that is named by this noun.
- der Vogel (grammatical masculine)
means a bird, regardless of its gender.
Also: der Esel, der Affe, der Wurm, der Hund, der Elch and many others.
Even der Mensch is grammatical masculine and means any human being
- die Katze (grammatical feminine)
means a cat, regardless of its gender.
Also: die Schlange, die Ziege, die Ente, die Maus, ...
- das Schwein (grammatical neuter)
means a pig, regardless of its gender.
Also: das Rind, das Kaninchen, das Kamel, das Chameleon, ...
For many species there are distinct words for adult male, adult female and non-adult individuals, and for some species there are additional names for castrated male individuals. Here are some examples:
- Species: das Schwein
adult male: der Eber
adult female: die Sau
young: das Ferkel
- Species: das Schaf
adult male: der Bock, der Widder
adult female: die Au, die Aue, die Zibbe
young: das Lamm
castrated male: der Hammel
- Species: das Pferd
adult male: der Hengst
adult female: die Stute
young: das Fohlen, das Füllen
castrated male: der Wallach
- Species: der Hirsch
adult male: der Bulle
adult female: die Hinde, die Hirschkuh
young: das Kalb
- Species: der Hase
adult male: der Rammler
adult female: die Zibbe
young: der Welpe
- Species: die Gämse
adult male: der Bock
adult female: die Geiß
young: das Kitz
But der Vogel does not belong to this group. Vogel is not the name of a species, but of a class. Chicken (das Huhn), goose (die Gans) and ducks (die Ente) are birds for witch German has distinct names for male and female individuals, but not for birds in general.
On the other hand you also should remember, that the biological gender is a property of a living being, not of the noun used to name it. For example he words die Frau feminine, das Weib neuter and der Trampel1 masculine can be used to name the very same awkward and lubberly female adult person:
Die Frau macht mich wahnsinnig, sie macht alles kaputt!
Das Weib macht mich wahnsinnig, es macht alles kaputt!
Der Trampel macht mich wahnsinnig, er macht alles kaputt!
Note, that the pronouns gender (in these examples: the word immediately after the comma) must always match with the gender of the noun to which it refers. So, although we are always talking about a woman, we somtimes have to refer to her with the German equivalent of "it" and even "he". THis is, because grammatical Gender and biological gender don't always have to match in German language (although they still often do).
1»Der Trampel« is a rare word, mainly used in southern regions of german speaking area. Although it is a grammatical masculine noun, it only can be used for female persons. It is a pejorative word that means a clumsy and lubberly female person of any age (including children) who have a tendency to destroy anything they touch.